Systems and methods for monitoring and enabling use of a medical instrument

ABSTRACT

Systems and methods monitor and enable the use of a medical instrument that is configured to be operated in a prescribed manner. The systems and methods employ a use register sized and configured to be carried by the medical instrument, which comprises a memory field for recording a start date and time at an instance of first operation of the medical instrument. The systems and methods also employ a use monitoring controller, which is adapted and configured to be coupled to the use register. The use monitoring controller includes a start validation function that compares the start date and time to a present real date and time and provides a start validation output based upon the comparison. The use monitoring controller also includes an enablement function that enables operation of the medical instrument only if the start validation output meets prescribed criteria.

RELATED APPLICATION

This application is a divisional of co-pending application Ser. No.10/202,447 filed on 24 Jul. 2002, which is a continuation-in-part ofco-pending U.S. patent application Ser. No. 09/935,908, filed Aug. 23,2001, which is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 09/645,662, filed Aug. 24, 2000, and entitled“Systems and Methods for Enhancing Blood Perfusion Using UltrasoundEnergy,” which are both incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to systems and methods for increasing bloodperfusion, e.g., in the treatment of myocardial infarction, strokes, andvascular diseases.

BACKGROUND OF THE INVENTION

High frequency (5 MHz to 7 MHz) ultrasound has been widely used fordiagnostic purposes. Potential therapeutic uses for ultrasound have alsobeen more recently suggested. For example, it has been suggested thathigh power, lower frequency ultrasound can be focused upon a blood clotto cause it to break apart and dissolve. The interaction between lowerfrequency ultrasound in the presence of a thrombolytic agent has alsobeen observed to assist in the breakdown or dissolution of thrombi. Theeffects of ultrasound upon enhanced blood perfusion have also beenobserved.

While the therapeutic potential of these uses for ultrasound has beenrecognized, their clinical promise has yet to be fully realized.Treatment modalities that can apply ultrasound in a therapeutic way aredesigned with the premise that they will be operated by trained medicalpersonnel in a conventional fixed-site medical setting. They assume thepresence of trained medical personnel in a non-mobile environment, whereelectrical service is always available. Still, people typicallyexperience the effects of impaired blood perfusion suddenly in publicand private settings. These people in need must be transported from thepublic or private settings to the fixed-site medical facility beforeultrasonic treatment modalities can begin. Treatment time (which isoften critical in the early stages of impaired blood perfusion) is lostas transportation occurs. Even within the fixed-site medical facility,people undergoing treatment need to be moved from one care unit toanother. Ultrasonic treatment modalities must be suspended while theperson is moved.

SUMMARY OF THE INVENTION

The invention provides systems and methods that monitor and enable theuse of a medical instrument that is configured to be operated in aprescribed manner.

According to one aspect of the invention, the systems and methods employa use register sized and configured to be carried by the medicalinstrument, which comprises a memory field for recording a start dateand time at an instance of first operation of the medical instrument.The systems and methods also employ a use monitoring controller, whichis adapted and configured to be coupled to the use register. The usemonitoring controller includes a start validation function that comparesthe start date and time to a present real date and time and provides astart validation output based upon the comparison. The use monitoringcontroller also includes an enablement function that enables operationof the medical instrument only if the start validation output meetsprescribed criteria.

According to another aspect of the invention, the systems and methodscomprise a use register that is sized and configured to be carried bythe medical instrument. The use register comprises a memory field forrecording a prescribed copyright notice. The systems and methods alsoinclude a use monitoring controller that is adapted and configured to becoupled to the use register. The use monitoring controller includes acopyright validation function that assesses the contents of the memoryfield and provides a copyright validation output based upon theassessment. The use monitoring controller also includes an enablementfunction that enables operation of the medical instrument only if thecopyright validation output meets prescribed criteria.

In one embodiment, the medical instrument comprises an ultrasound energyapplicator that includes an ultrasound transducer adapted and configuredto be coupled to an ultrasound generator for operation. In thisembodiment, the use register is sized and configured to be carried bythe ultrasound applicator.

Other features and advantages of the inventions are set forth in thefollowing specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a system for transcutaneously applyingultrasound energy to affect increased blood perfusion.

FIG. 2 is an enlarged exploded perspective view of an ultrasoundapplicator that forms a part of the system shown in FIG. 1.

FIG. 3 is an enlarged assembled perspective view of the ultrasoundapplicator shown in FIG. 2.

FIG. 4 is a side section view of the acoustic contact area of theultrasound applicator shown in FIG. 2.

FIG. 5 is a view of the applicator shown in FIG. 2 held by astabilization assembly in a secure position overlaying the sternum of apatient, to transcutaneously direct ultrasonic energy, e.g., toward thevasculature of the heart.

FIG. 6 is a side elevation view, with portions broken away and insection, of an acoustic stack that can be incorporated into theapplicator shown in FIG. 2.

FIG. 7 is a side elevation view, with portions broken away and insection, of an acoustic stack that can be incorporated into theapplicator shown in FIG. 2.

FIG. 8 a to 8 c graphically depict the technical features of a frequencytuning function that the system shown in FIG. 1 can incorporate.

FIG. 9 graphically depicts the technical features of a power rampingfunction that the system shown in FIG. 1 can incorporate.

FIG. 10 is a schematic view of a controller that the system shown inFIG. 1 can incorporate, which includes a frequency tuning function, apower ramping function, an output power control function, and a usemonitoring function.

FIG. 11 is a diagrammatic view of a use register chip that forms a partof the use monitoring function shown in FIG. 10.

FIG. 12 is a diagrammatic flow chart showing the technical features ofthe use monitoring function shown in FIG. 10.

The invention may be embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The various aspects of the invention will be described in connectionwith the therapeutic indication of providing increased blood perfusionby the transcutaneous application of ultrasonic energy. That is becausethe features and advantages of the invention are well suited to thistherapeutic indication. Still, it should be appreciated that manyaspects of the invention can be applied to achieve other diagnostic ortherapeutic objectives as well.

Furthermore, in describing the various aspects of the invention in thecontext of the illustrated embodiment, the region targeted for anincrease in blood perfusion is the thoracic cavity (i.e., the spacewhere the heart and lungs are contained). It should be appreciated,however, that the features of invention have application in otherregions of the body, too, for example, in the arms, legs, or brain.

I. System for Providing Noninvasive Ultrasound-Assisted Blood Perfusion

FIG. 1 schematically shows a compact, portable therapeutic system 10that makes it possible to treat a person who needs or who is likely toneed an increase in the flow rate or perfusion of circulating blood.

The system 10 includes durable and disposable equipment and materialsnecessary to treat the person at a designated treatment location. Inuse, the system 10 affects increased blood perfusion by transcutaneouslyapplying ultrasonic energy.

As FIG. 1 shows, the system 10 includes at the treatment location anultrasound generating machine 16. The system 10 also includes at thetreatment location at least one ultrasound applicator 18, which iscoupled to the machine 16 during use. As FIG. 5 shows, the system 10also includes an assembly 12 for use with the applicator 18 to stabilizethe position of the applicator 18 on a patient for hands-free use. Inthe illustrated embodiment (see FIG. 5), the applicator 18 is securedagainst movement on a person's thorax, overlaying the sternum, to directultrasonic energy toward the vasculature of the heart.

The location where treatment occurs can vary. It can be a traditionalclinical setting, where support and assistance by one or more medicallytrained care givers are immediately available to the person, such asinside a hospital, e.g., in an emergency room, catheter lab, operatingroom, or critical care unit. However, due to the purposeful design ofthe system 10, the location need not be confined to a traditionalclinical setting. The location can comprise a mobile setting, such as anambulance, helicopter, airplane, or like vehicle used to convey theperson to a hospital or another clinical treatment center. The locationcan even comprise an everyday, public setting, such as on a cruise ship,or at a sports stadium or airport, or a private setting, such as in aperson's home, where the effects of low blood perfusion can arise.

By purposeful design of durable and disposable equipment, the system 10can make it possible to initiate treatment of a reduced blood perfusionincident in a non-clinical, even mobile location, outside a traditionalmedical setting. The system thereby makes effective use of the criticaltime period before the person enters a hospital or another traditionalmedical treatment center.

The features and operation of the system 10 will now be described ingreater detail.

A. The Ultrasound Generator

FIG. 1 shows a representative embodiment of the ultrasound generatingmachine 16. The machine 16 can also be called an “ultrasound generator.”The machine 16 is intended to be a durable item capable of long term,maintenance free use.

As shown in FIG. 1, the machine 16 can be variously sized and shaped topresent a lightweight and portable unit, presenting a compact footprintsuited for transport. The machine 16 can be sized and shaped to bemounted at bedside, or to be placed on a table top or otherwise occupy arelatively small surface area. This allows the machine 16 to travel withthe patient within an ambulance, airplane, helicopter, or othertransport vehicle where space is at a premium. This also makes possiblethe placement of the machine 16 in a non-obtrusive way within a privatehome setting, such as for the treatment of chronic angina.

In the illustrated embodiment, the machine 16 includes a chassis 22,which, for example, can be made of molded plastic or metal or both. Thechassis 22 houses a module 24 for generating electric signals. Thesignals are conveyed to the applicator 18 by an interconnect 30 to betransformed into ultrasonic energy. A controller 26, also housed withinthe chassis 22 (but which could be external of the chassis 22, ifdesired), is coupled to the module 24 to govern the operation of themodule 24. Further desirable technical features of the controller 26will be described later.

The machine 16 also preferably includes an operator interface 28. Usingthe interface 28, the operator inputs information to the controller 26to affect the operating mode of the module 24. Through the interface 28,the controller 26 also outputs status information for viewing by theoperator. The interface 28 can provide a visual readout, printer output,or an electronic copy of selected information regarding the treatment.The interface 28 is shown as being carried on the chassis 22, but itcould be located external of the chassis 22 as well.

The machine 16 includes a power cord 14 for coupling to a conventionalelectrical outlet, to provide operating power to the machine 16. Themachine 16 can also include a battery module (not shown) housed withinthe chassis 22, which enables use of the machine 16 in the absence orinterruption of electrical service. The battery module can compriserechargeable batteries, that can be built in the chassis 22 or,alternatively, be removed from the chassis 22 for recharge. Likewise,the battery module (or the machine 16 itself) can include a built-in orremovable battery recharger. Alternatively, the battery module cancomprise disposable batteries, which can be removed for replacement.

Power for the machine 16 can also be supplied by an external batteryand/or line power module outside the chassis 22. The battery and/or linepower module is releasably coupled at time of use to the componentswithin the chassis 22, e.g., via a power distribution module within thechassis 22.

The provision of battery power for the machine 16 frees the machine 16from the confines surrounding use of conventional ultrasound equipment,caused by their dependency upon electrical service. This feature makesit possible for the machine 16 to provide a treatment modality thatcontinuously “follows the patient,” as the patient is being transportedinside a patient transport vehicle, or as the patient is being shuttledbetween different locations within a treatment facility, e.g., from theemergency room to a holding area within or outside the emergency room.

In a representative embodiment, the chassis 22 measures about 12inches×about 8 inches×about 8 inches and weighs about 9 pounds.

B. The Ultrasound Applicator

As shown in FIG. 5, the applicator 18 can also be called the “patientinterface.” The applicator 18 comprises the link between the machine 16and the treatment site within the thoracic cavity of the personundergoing treatment. The applicator 18 converts electrical signals fromthe machine 16 to ultrasonic energy, and further directs the ultrasonicenergy to the targeted treatment site.

Desirably, the applicator 18 is intended to be a disposable item. Atleast one applicator 18 is coupled to the machine 16 via theinterconnect 30 at the beginning a treatment session. The applicator 18is preferably decoupled from the interconnect 30 (as FIG. 1 shows) anddiscarded upon the completing the treatment session. However, ifdesired, the applicator 18 can be designed to accommodate more than asingle use.

As FIGS. 2 and 3 show, the ultrasound applicator 18 includes a shapedmetal or plastic body 38 ergonomically sized to be comfortably graspedand manipulated in one hand. The body 38 houses and supports at leastone ultrasound transducer 40 (see FIG. 3).

In the illustrated embodiment, the ultrasound transducer 40 comprises anacoustic stack 20. The acoustic stack 20 comprises a front mass piece32, a back mass piece 34, and one or more piezoelectric elements 36,which are bolted together. The back mass piece 34 comprises an annularring of material having relatively high acoustic impedance, e.g., steelor stainless steel. “Acoustic impedance” is defined as the product ofthe density of the material and the speed of sound.

The front mass piece 32 comprises a cone-shaped piece of material havingrelatively low acoustic impedance, e.g., aluminum or magnesium. Thepiezoelectric elements 36 are annular rings made of piezoelectricmaterial, e.g., PZT. An internally threaded hole or the like receives abolt 42 that mechanically biases the acoustic stack 20. A bolt 42 thatcan be used for this purpose is shown in U.S. Pat. No. 2,930,912. Thebolt 42 can extend entirely through the front mass piece 32 or, the bolt42 can extend through only a portion of the front mass piece 32 (seeFIG. 7).

In an alternative embodiment (see FIG. 6), the acoustic stack 20′ of atransducer 40′ can comprise a single piezoelectric element 36′sandwiched between front and back mass pieces 32′ and 34′. In thisarrangement, the back mass piece 34′ is electrically insulated from thefront mass piece 32′ by, e.g., an insulating sleeve and washer 44.

The piezoelectric element (s) 36/36′ have electrodes 46 (see FIG. 2) onmajor positive and negative flat surfaces. The electrodes 46electrically connect the acoustic stack 20 of the transducer 40 to theelectrical signal generating module 24 of the machine 16. Whenelectrical energy at an appropriate frequency is applied to theelectrodes 46, the piezoelectric elements 36/36′ convert the electricalenergy into mechanical (i.e., ultrasonic) energy in the form ofmechanical vibration.

The mechanical vibration created by the transducer 40/40′ is coupled toa patient through a transducer bladder 48, which rests on a skinsurface. The bladder 48 defines a bladder chamber 50 (see FIG. 4)between it and the front mass piece 32. The bladder chamber 50 spacesthe front mass piece 32 a set distance from the patient's skin. Thebladder chamber 50 accommodates a volume of an acoustic coupling medialiquid, e.g., liquid, gel, oil, or polymer, that is conductive toultrasonic energy, to further cushion the contact between the applicator18 and the skin. The presence of the acoustic coupling media also makesthe acoustic contact area of the bladder 48 more conforming to the localskin topography.

Desirably, an acoustic coupling medium is also applied between thebladder 48 and the skin surface. The coupling medium can comprise, e.g.,a gel material (such as AQUASONIC® 100, by Parker Laboratories, Inc.,Fairfield, N.J.). The external material can possess sticky or tackyproperties, to further enhance the securement of the applicator 18 tothe skin.

In the illustrated embodiment, the bladder 48 and bladder chamber 50together form an integrated part of the applicator 18. Alternatively,the bladder 48 and bladder chamber 50 can be formed by a separate moldedcomponent, e.g., a gel or liquid filled pad, which is suppliedseparately. A molded gel filled pad adaptable to this purpose is theAQUAFLEX® Ultrasound Gel Pad sold by Parker Laboratories (Fairfield,N.J.).

In a representative embodiment, the front mass piece 32 of the acousticstack 20 measures about 2 inches in diameter, whereas the acousticcontact area formed by the bladder 48 measures about 4 inches indiameter. An applicator 18 that presents an acoustic contact area oflarger diameter than the front mass piece 32 of the transducer 40 makespossible an ergonomic geometry that enables single-handed manipulationduring set-up, even in confined quarters, and further provides (with theassembly 12) hands-free stability during use. In a representativeembodiment, the applicator 18 measures about 4 inches in diameter aboutthe bladder 48, about 4 inches in height, and weighs about one pound.

An O-ring 52 (see FIG. 4) is captured within a groove 54 in the body 38of the applicator 18 and a groove 84 on the front mass piece 32 of thetransducer 40. The o-ring 52 seals the bladder chamber 50 and preventsliquid in the chamber 50 from contacting the sides of the front masspiece 32. Thus, as FIG. 4 shows, only the outer surface of the frontmass piece 32 is in contact with the acoustic coupling medium within thechamber 50.

Desirably, the material of the O-ring 52 is selected to possesselasticity sufficient to allow the acoustic stack 20 of the transducer40 to vibrate freely in a piston-like fashion within the transducer body38. Still, the material of the O-ring 52 is selected to be sturdy enoughto prevent the acoustic stack 20, while vibrating, from popping out ofthe grooves 54 and 84.

In a representative embodiment, the O-ring 52 is formed from nitrilerubber (Buna-N) having a hardness of about 30 Shore A to about 100 ShoreA. Preferably, the O-ring 52 has a hardness of about 65 Shore A to about75 Shore A.

The bladder 48 is stretched across the face of the bladder chamber 50and is preferably also locked in place with another O-ring 56 (see FIG.4). A membrane ring may also be used to prevent the O-ring 56 frompopping loose. The membrane ring desirably has a layer or layers of softmaterial (e.g., foam) for contacting the skin.

Localized skin surface heating effects may arise by the presence of airbubbles trapped between the acoustic contact area (i.e., the surface ofthe bladder 48) and the individual's skin. In the presence of ultrasonicenergy, the air bubbles vibrate, and thereby may cause cavitation andattendant conductive heating effects at the skin surface. To minimizethe collection of air bubbles along the acoustic contact area, thebladder 48 desirably presents a flexible, essentially flat radiatingsurface contour where it contacts the individual's skin (see FIG. 4), ora flexible, outwardly bowed or convex radiating surface contour (i.e.,curved away from the front mass piece) where it contacts with orconducts acoustic energy to the individual's skin. Either a flexibleflat or convex surface contour can “mold” evenly to the individual'sskin topography, to thereby mediate against the collection andconcentration of air bubbles in the contact area where skin contactoccurs.

To further mediate against cavitation-caused localized skin surfaceheating, the interior of the bladder chamber 50 can include a recessedwell region 58 surrounding the front mass piece 32. The well region 58is located at a higher gravity position than the plane of the front masspiece 32. Air bubbles that may form in fluid located in the bladderchamber 50 are led by gravity to collect in the well region 58 away fromthe ultrasonic energy beam path.

The front mass piece 32 desirably possesses either a flat radiatingsurface (as FIG. 4 shows) or a convex radiating surface (as FIG. 7shows). The convex radiation surface directs air bubbles off theradiating surface. The radiating surface of the front mass piece mayalso be coated with a hydrophilic material 60 (see FIG. 4) to preventair bubbles from sticking.

The transducer 40 may also include a reflux valve/liquid inlet port 62.

The interconnect 30 carries a distal connector 80 (see FIG. 2), designedto easily plug into a mating outlet in the applicator 18. A proximalconnector 82 on the interconnect 30 likewise easily plugs into a matingoutlet on the chassis 22 (see FIG. 1), which is itself coupled to thecontroller 26. In this way, the applicator 18 can be quickly connectedto the machine 16 at time of use, and likewise quickly disconnected fordiscard once the treatment session is over. Other quick-connect couplingmechanisms can be used. It should also be appreciated that theinterconnect 30 can be hard wired as an integrated component to theapplicator 18 with a proximal quick-connector to plug into the chassis22, or, vice versa, the interconnect 30 can be hard wired as anintegrated component to the chassis 22 with a distal quick-connector toplug into the applicator 18.

As FIG. 5 shows, the stabilization assembly 12 allows the operator totemporarily but securely mount the applicator 18 against an exteriorskin surface for use. In the illustrated embodiment, since the treatmentsite exists in the thoracic cavity, the attachment assembly 54 isfashioned to secure the applicator 18 on the person's thorax, overlayingthe sternum or breastbone, as FIG. 5 shows.

The assembly 12 can be variously constructed. As shown in FIG. 5, theassembly 12 comprises straps 90 that pass through brackets 92 carried bythe applicator 18. The straps 90 encircle the patient's neck andabdomen.

Just as the applicator 18 can be quickly coupled to the machine 16 attime of use, the stabilization assembly 12 also preferably makes thetask of securing and removing the applicator 18 on the patient simpleand intuitive. Thus, the stabilization assembly 12 makes it possible tosecure the applicator 18 quickly and accurately in position on thepatient in cramped quarters or while the person (and the system 10itself) is in transit.

Desirably, when used to apply ultrasonic energy transcutaneously in thethoracic cavity to the heart, the front mass piece 32 is sized todeliver ultrasonic energy in a desired range of fundamental frequenciesto substantially the entire targeted region (e.g., the heart). Generallyspeaking, the fundamental frequencies of ultrasonic energy suited fortranscutaneous delivery to the heart in the thoracic cavity to increaseblood perfusion can lay in the range of about 500 kHz or less.Desirably, the fundamental frequencies for this indication lay in afrequency range of about 20 kHz to about 100 kHz, e.g., about 27 kHz.

II. Controlling the Application of Ultrasound Energy

To achieve the optimal application of ultrasound energy and the optimaltherapeutic effect, the application of ultrasound energy shoulddesirably incorporate one or more of the following features: (1) choice,or tuning, of the output frequency, (2) power ramping, (3) output powercontrol, and (4) pulsed power.

A. Tuning of Output Frequency

Depending upon the treatment parameters and outcome desired, thecontroller 26 can operate a given transducer 40 at a fundamentalfrequency below about 50 kHz, or in a fundamental frequency rangebetween about 50 kHz and about 1 MHz, or at fundamental frequenciesabove 1 MHz.

A given transducer 40 can be operated in either a pulsed or a continuousmode, or in a hybrid mode where both pulsed and continuous operationoccurs in a determined or random sequence at one or more fundamentalfrequencies.

The applicator 18 can include multiple transducers 40 (or multipleapplicators 18 can be employed simultaneously for the same effect),which can be individually conditioned by the controller 26 for operationin either pulsed or continuous mode, or both. For example, the multipletransducers 40 can all be conditioned by the controller 26 for pulsedmode operation, either individually or in overlapping synchrony.Alternatively, the multiple transducers 40 can all be conditioned by thecontroller 26 for continuous mode operation, either individually or inoverlapping synchrony. Still alternatively, the multiple transducers 40can be conditioned by the controller 26 for both pulsed and continuousmode operation, either individually or in overlapping synchrony.

One or more transducers 40 within an array of transducers 40 can also beoperated at different fundamental frequencies. For example, one or moretransducers 40 can be operated at about 25 kHz, while another one ormore transducers 40 can be operated at about 100 kHz. More than twodifferent fundamental frequencies can be used, e.g., about 25 kHz, about50 kHz, and about 100 kHz.

Operation at different fundamental frequencies provides differenteffects. For example, given the same power level, at about 25 kHz, morecavitation effects are observed to dominate, while above 500 kHz, moreheating effects are observed to dominate.

The controller 26 can trigger the fundamental frequency output accordingto time or a physiological event (such as ECG or respiration).

A given transducer 40 can be operated at a frequency within a certainrange of frequencies suitable to the transducer 40. The optimalfrequency for a given treatment is dependent on a number of factors,e.g., the magnitude of the fill volume of the bladder chamber 50; thecharacteristics of the acoustic coupling between the acoustic contactarea (i.e., bladder 48) and the patient's skin; the morphology of thepatient (e.g., size, weight, girth) which affect the transmission ofultrasound energy through the skin and within the body; the acousticload impedance seen by the transducer 40.

As FIG. 10 shows, the controller 26 desirably includes a tuning function64. The tuning function 64 selects an optimal frequency at the outset ofeach treatment session, taking into account at least some of theabove-listed factors. In the illustrated embodiment (see FIGS. 8A to8C), the tuning function sweeps the output frequency within apredetermined range of frequencies (f-start to f-stop). The frequencysweep can be and desirably is done at an output power level that islower than the output power level of treatment (see FIG. 9). Thefrequency sweep can also be done in either a pulsed or a continuousmode, or in a hybrid mode. An optimal frequency of operation is selectedbased upon one or more parameters sensed during the sweeping operation.

As FIG. 8A shows, the frequency sweep can progress from a lowerfrequency (f-start) to a higher frequency (f-stop), or vice versa. Thesweep can proceed on a linear basis (as FIG. 8A also shows), or it canproceed on a non-linear basis, e.g., logarithmically or exponentially orbased upon another mathematical function. The range of the actualfrequency sweep may be different from the range that is used todetermine the frequency of operation. For instance, the frequency spanused for the determination of the frequency of operation may be smallerthan the range of the actual sweep range.

In one frequency selection approach (see FIGS. 8A and 8C), whilesweeping frequencies, the tuning function 64 adjusts the output voltageand/or current to maintain a constant output power level (p-constant).The function 64 also senses changes in transducer impedance (see FIG.8B)—Z-min to Z-max—throughout the frequency sweep. In this approach (seeFIG. 8B), the tuning function 64 selects as the frequency of operationthe frequency (f-tune) where, during the sweep, the minimum magnitude oftransducer impedance (Z-min) is sensed. Typically, this is about thesame as the frequency of maximum output current (I), which in turn, isabout the same as the frequency of minimum output voltage (V).

In an alternative frequency selection approach, the tuning function 64can select as the frequency of operation the frequency where, during thesweep, the maximum of real transducer impedance (Z) occurs, where:|Z|=√{square root over ((R)}² +X ²)

-   -   and where |Z| is the absolute value of the transducer impedance        (Z), which derived according to the following expression:        Z=R+iX

where R is the real part, and X is the imaginary part.

In another alternative frequency selection approach, while sweeping thefrequencies, the tuning function 64 can maintain a constant outputvoltage. In this approach, the tuning function 64 can select as thefrequency of operation the frequency where, during the sweep, themaximum output power occurs. Alternatively, the tuning function 64 canselect as the frequency of operation the frequency where, during thesweep, the maximum output current occurs.

B. Power Ramping

As before described, the tuning function 64 desirably operates an outputpower level lower than the output power level of treatment. In thisarrangement, once the operating frequency has been selected, the outputpower level needs to be increased to the predetermined output level tohave the desired therapeutic effect.

In the illustrated embodiment (see FIG. 10), the controller 26 includesa ramping function 66. The ramping function 66 (see FIG. 9) causes agradual ramp up of the output power level from the power level at whichthe tuning function 64 is conducted (e.g., 5 W) to the power level atwhich treatment occurs (e.g., 25 W). The gradual ramp up decreases thepossibility of unwanted patient reaction to the ultrasound exposure.Further, a gradual ramp up is likely to be more comfortable to thepatient than a sudden onset of the full output power.

In a desired embodiment, the ramping function 66 increases power at arate of about 0.01 W/s to about 10 W/s. A particularly desired rampingrate is between about 0.1 W/s to about 5 W/s. The ramping function 66desirably causes the ramp up in a linear fashion (as FIG. 9 shows).However, the ramping function can employ non-linear ramping schemes,e.g., logarithmic or according to another mathematical function.

C. Output Power Control

Also depending upon the treatment parameters and outcome desired, thecontroller 26 can operate a given transducer 40 at a prescribed powerlevel, which can remain fixed or can be varied during the treatmentsession. The controller 26 can also operate one or more transducers 40within an array of transducers 40 (or when using multiple applicators18) at different power levels, which can remain fixed or themselves varyover time.

The parameters affecting power output take into account the output ofthe signal generator module; the physical dimensions and construction ofthe applicator; and the physiology of the tissue region to whichultrasonic energy is being applied.

During a given treatment session, the transducer impedance may vary dueto a number of reasons, e.g., transducer heating, changes in acousticcoupling between the transducer and patient, and/or changes in thetransducer bladder fill volume due to degassing and/or leaks. In theillustrated embodiment (see FIG. 10), the controller 26 includes anoutput power control function 68. The output power control function 68holds the output power constant, despite changes in transducer impedancewithin a predetermined range. If the transducer falls out of thepredetermined range, for instance, due to an open or a short circuit,the controller 26 shutdowns the generator ultrasound module 24 anddesirably sounds an alarm.

Governed by the output power control function 68, as the transducerimpedance increases, the output voltage is increased to hold the poweroutput constant. Should the output voltage reach a preset maximumallowable value, the output power will decrease, provided the transducerimpedance remains within its predetermined range. As the transducerimpedance subsequently drops, the output power will recover, and thefull output power level will be reached again.

Governed by the output power control function 68, as the transducerimpedance decreases, the output current is increased to hold the poweroutput constant. Should the output current reach a preset maximumallowable value, the output power will decrease until the impedanceincreases, again, and will allow full output power.

In addition to the described changes in the output voltage and currentto maintain a constant output power level, the output power controlfunction 68 can vary the frequency of operation slightly upward ordownward to maintain the full output power level within the allowablecurrent and voltage limits.

D. Pulsed Power Mode

The application of ultrasonic energy in a pulsed power mode can serve toreduce the localized heating effects that can arise due to operation ofthe transducer 40.

During the pulsed power mode, ultrasonic energy is applied at a desiredfundamental frequency or within a desired range of fundamentalfrequencies at the prescribed power level or range of power levels (asdescribed above, to achieve the desired physiologic effect) in aprescribed duty cycle (DC) (or range of duty cycles) and a prescribedpulse repetition frequency (PRF) (or range of pulse repetitionfrequencies). Desirably, the pulse repetition frequency (PRF) is betweenabout 20 Hz to about 50 Hz (i.e, between about 20 pulses a second toabout 50 pulses a second).

The duty cycle (DC) is equal to the pulse duration (PD) divided by oneover the pulse repetition frequency (PRF). The pulse duration (PD) isthe amount of time for one pulse. The pulse repetition frequency (PRF)represents the amount of time from the beginning of one pulse to thebeginning of the next pulse. For example, given a pulse repetitionfrequency (PRF) of 30 Hz (30 pulses per second) and a duty cycle of 25%yields a pulse duration (PD) of approximately 8 msec. At these settings,the system outputs an 8 msec pulse followed by a 25 msec off period 30times per second.

Given a pulse repetition frequency (PRF) selected at 25 Hz and a desiredfundamental frequency of 27 kHz delivered in a power range of betweenabout 15 to 30 watts, a duty cycle of about 50% or less meets thedesired physiologic objectives in the thoracic cavity, with lessincidence of localized conductive heating effects compared to acontinuous application of the same fundamental frequency and powerlevels over a comparable period of time. Given these operatingconditions, the duty cycle desirably lays in a range of between about10% and about 35%.

III. Monitoring Use of the Transducer

To protect patients from the potential adverse consequences occasionedby multiple use, which include disease transmission, or material stressand instability, or decreased or unpredictable performance, thecontroller 26 desirably includes a use monitoring function 70 (see FIG.10) that monitors incidence of use of a given transducer 40.

In the illustrated embodiment, the transducer 40 carries a use register72 (see FIG. 4). The use register 72 is configured to record informationbefore, during, and after a given treatment session. The use register 72can comprise a solid state micro-chip, ROM, EEROM, EPROM, or nonvolatile RAM (NVRAM) carried by the transducer 40.

The use register 72 is initially formatted and programmed by themanufacturer of the system to include memory fields. In the illustratedembodiment (see FIG. 11), the memory fields of the use register are oftwo general types: Write Many Memory Fields 74 and Write-Once MemoryFields 76. The Write Many Memory Fields 74 record information that canbe changed during use of the transducer 40. The Write-Once Memory Fields76 record information that, once recorded, cannot be altered.

The specific information recorded by the Memory Fields 74 and 76 canvary. The following table exemplifies typical types of information thatcan be recorded in the Write Many Memory Fields 74. Size Field NameDescription Location (Byte) Treatment If a transducer has been 0 1Complete used for a prescribed maximum treatment time (e.g., 60minutes), the treatment complete flag is set to 1 otherwise it is zero.Prescribed This is the allowable usage 1-2 2 Maximum time of thetransducer. Treatment This is set by the Time manufacturer anddetermines (Minutes) at what point the Treatment Complete flag is setto 1. Elapsed Initialized to zero. This 3-4 2 Usage Time area is thenincremented (Minutes) every minute that the system is transmittingultrasound energy. This area keeps track of the amount of time that thetransducer has been used. When this time reaches the Prescribed MaximumTreatment Time, the Treatment Complete flag is set to 1. Transducer Thisis an area that could 5-6 2 Frequency be used to prescribe theoperational frequency of the transducer, rather than tuning thetransducer to an optimal frequency, as above described. In the latterinstance, this area shows the tuned frequency once the transducer hasbeen tuned. Average The system reads and 7-8 2 Power accumulates thedelivered (Watts) power throughout the procedure. Every minute, theaverage power number is updated in this area from the system, at thesame time the Elapsed Usage Time is updated. when the Usage time clockis updated. This means that the average power reading could be off by amaximum of 59 seconds if the treatment is stopped before the TreatmentComplete flag is set. This average power can be used as a check to makesure that the system was running at full power during the procedure.Applicator Use Register CRC. This  9-10 2 CRC desirably uses the sameCRC algorithm used to protect the controller ROM. Copyright Desirably,the name of the 11-23 11 Notice manufacturer is recorded in this area.Other information can be recorded here as well.

The on/off cycles of ultrasound transmission could affect the accuracyof the recorded power levels because of the variance of the power levelsdue to ramping function 66. For this reason it may be advantageous toalso record the number of on/off cycles of ultrasound transmission. Thiswill help explain any discrepancies in the average power reading. Itmight also allow the identification of procedural problems with systemuse.

Each use register 72 can be assigned a unique serial number that couldbe used to track transducers in the field. This number can be read bythe use monitoring function 70 if desired.

The following table exemplifies typical types of information that can berecorded in the Write-Once Memory Fields 76. Size Field Name Description(Bytes) Start Date Time Once the system has tuned the transducer andstarted to transmit ultrasound, the current date and time are written tothis area. This area is then locked, which prevents the data fromever-being changed. Tuned Frequency The tuned frequency is written tothis location when the Start Date and Time is set. This prevents thisinformation from being written over on subsequent tunes (if necessary).

As FIG. 12 shows, when a transducer 40 is first coupled to the machine16, and prior to enabling the conveyance of ultrasound energy to thetransducer 40, the use monitoring function 70 prompts the use register72 to output resident information recorded in the memory fields.

The use monitoring function 70 compares the contents of the CopyrightNotice field to a prescribed content. In the illustrated embodiment, theprescribed content includes information contained in the CopyrightNotice field of the Write Many Memory Fields 74. The prescribed contenttherefore includes the name of the manufacturer, or other indiciauniquely associated with the manufacture. If the prescribed content ismissing, the use monitoring function 70 does not enable use of thetransducer 40, regardless of the contents of any other memory field. Thetransducer 40 is deemed “invalid.” In this way, a manufacturer canassure that only transducers meeting its design and quality controlstandards are operated in association with the machine 16.

If the contents of the Copyright Notice field match, the use monitoringfunction 70 compares the digital value residing in the TreatmentComplete field of the Write Many Memory Fields 74 to a set value thatcorresponds to a period of no prior use or a prior use less than thePrescribed Maximum Treatment Time—i.e., in the illustrated embodiment, azero value. A different value (i.e., a 1 value) in this field indicatesa period of prior use equal to or greater than the Prescribed MaximumTreatment Time. In this event, the use monitoring function 70 does notenable use of the transducer 40. The transducer 40 is deemed “invalid.”

If a value of zero resides in the Treatment Complete field, the usemonitoring function 70 compares the date and time data residing in theWrite-Once Start Date and Time field to the current date and timeestablished by a Real Time Clock. If the Start Date and Time is morethan a prescribed time before the Real Time (e.g., 4 hours), thecontroller does not enable use of the transducer 40. The transducer 40is deemed “invalid.”

If the Start Date and Time field is empty, or if it is less than theprescribed time before the Real Time, the use monitoring function 70deems the transducer 40 to be “valid” (providing the preceding othercriteria have been met). The use monitoring function 70 reports a validtransducer to the controller 26, which initiates the tuning function 64.If the Start Date and Time field is empty, once the tuning function 64is completed, the controller prompts the use monitoring function 70 torecords the current date and time in the Start Date and Time Field, aswell as the selected operating frequency in the Tuned Frequency field.The controller 26 then proceeds to execute the ramping function 66 and,then, execute the prescribed treatment protocol.

If the Start Date and Time field is not empty (indicating a permittedprior use), once the tuning function 64 is completed, the controller 26immediately proceeds with the ramping function 66 and, then, execute thetreatment protocol.

During use of the transducer 49 to accomplish the treatment protocol,the use monitoring function 70 periodically updates the Elapsed UsageTime field and Average Power field (along with other Many Write MemoryFields). Once the Treatment Complete flag is set to a 1 value(indicating use of the transducer beyond the Prescribed MaximumTreatment Time), the use monitoring function 70 interrupts the supply ofultrasound energy to the transducer. The transducer 40 is deemed“invalid” for subsequent use. The use monitoring function 70 can alsogenerate an output that results in a visual or audible alarm, informingthe operator that the transducer 40 cannot be used.

The information recorded in the use register 72 can also be outputted tomonitor use and performance of a given transducer 40. Other sensors canbe used, e.g., a temperature sensor 78 carried on the front mass piece32 (see FIG. 4), in association with the use register.

As described, the use register 72 allows specific pieces of informationto be recorded before, during and after a treatment is complete.Information contained in the use register 72 is checked before allowinguse of a given transducer 40. The use register 72 ensures that only atransducer 40 having the desired design and performance criteriaimparted by the manufacturer can be used. In addition, the use register72 can be used to “lock out” a transducer 40 and prevent it from beingused in the future. The only way the transducer 40 could be reused is toreplace the use register 72 itself. However, copying the architecture ofthe use register 72 (including the contents of the Copyright Messagefield required for validation) itself constitutes a violation of themanufacturer's copyright in a direct and inescapable way.

Various features of the invention are set forth in the following claims.

1. A system for monitoring and enabling use of a medical instrument that is configured to be operated in a prescribed manner, the system comprising a use register sized and configured to be carried by the medical instrument and comprising a memory field for recording a start date and time at an instance of first operation of the medical instrument, and a use monitoring controller adapted and configured to be coupled to the use register including a start validation function that compares the start date and time to a present real date and time and provides a start validation output based upon the comparison, and an enablement function that enables operation of the medical instrument only if the start validation output meets prescribed criteria. 